base plate of heasink

[mik]

How important is dimension of base plate of the heatsink

[jan.didden]

Quite important!

Without it, the fins would just hang there in mid air, wouldn't they? Also, where would you attach the transistors?

(Sorry moderators, couldn't resist this one)


Jan Didden

[jan.didden]

Seriously now,

I haven't really studied it, but two things come to mind, size and thickness. Thickness is important to spread the heat quickly to the outlying fins. Therefore, I think that the larger the sink, the thicker the baseplate should be. But I have no quick numbers.

As for size, obviously if you need more cooling cap, you need more real estate to radiate and/or conduct the heat to the ambient air. There is a limit to the number of fins you can put on an inch and the size of the fins with respect to their distance, because if you put them too close they will heat each other, unless you use forced air. So, closely-spaced fins need forced air to be effective. With natural convection you need to get larger area with higher capacity. But this is all common sense.

Bottom line, as I see it, thicker baseplate will make the sink more effective all other things being equal.
Does this help you?

Jan Didden

[mik]

Jan, thanks for the answer!
It was my fault because I didn't formulated question very well.
I found some heatsinks at italian shop of electronics components with good price .Dimensions are: LXW (1000mmX190) Fins are 50mm long and base is 5mm so thats why I asked about base plate.

[Nickolas K.]

I think that the larger the sink, the thicker the baseplate should be.

I'm not sure it's true.
Just check the dimension of the famous Fischer SK 157 and you'll get my point.

Regards,

Nick

[jan.didden]

Well, my argument was that the larger the sink, the less "heat resistance" you want to quickly spread the heat to the outlying fins, if you want max efficiency for the size. That means thicker baseplate.

The fact the there exist some heatsinks with size a and thickness b doesn't really tell me anything, except that there probably is a market for heatsinks size a thickness b...

Jan Didden

[jan.didden]

Originally posted by mik
Jan, thanks for the answer!
It was my fault because I didn't formulated question very well.
I found some heatsinks at italian shop of electronics components with good price .Dimensions are: LXW (1000mmX190) Fins are 50mm long and base is 5mm so thats why I asked about base plate.

Just a gut feeling, seems these are pretty good in this repect. Fins are a bit high though. How much space between the fins?

Jan Didden

[UrSv]

Sounds like a good sized heatsink to me. Fin length is just fine (IMHO) and to some extent I think the longer the better (to a certain point of course) and the reason for fins being around 40 mm or less is mainly due to extrusion limitations and such but performance, as far as I know, will be better with longer fins but the prices will not be...

Depending on the heat you need to dissipate and how you apply it I think the sink will be just fine. Try to spread the "heat entry point" across the width to work around the base plate thickness which is not too small but not very large either...

/UrSv

[Peter Daniel]

The thickness of base plate is important in case the heat sinks make the part of a chassis and are exposed. You have to drill holes through them to mount devices. If the plate is not thick enough the holes would be visible (if you decide to tap the holes, they have to be even deeper).

[UrSv]

Oops, follow up with mounting tips...

I use hex (allen key?) or torx black shallow head bolts that I can fit from the outside and then nuts ion the inside for that problem making sure to drill EXACTLY between fins. There will be a bolt head but it will be black and be inconspicous...

/UrSv